U.S. Pat. No. 3,999,947 describes a sensor having two electrodes and a heater element on a carrier for measuring hydrocarbon mixtures. The electrodes are disposed at a great distance from one another and are covered with a gas-sensitive element which splits the hydrocarbon material into ions and electrons. The gas-sensitive layer is difficult to manufacture and can be used only in the low temperature region. At high temperatures, chemical processes take place in the gas-sensitive layer which tend to destroy the layer and gum up the electrodes. Thus, such sensors cannot be used at high temperatures.